1. Technical Field
The present invention relates to methods and apparatus for determining cerebral oxygenation in general, and to those operable to determine the rate of oxygen desaturation in particular.
2. Background Information
Surgical procedures that involve circulatory arrest can include a risk of neurological sequelae, including those associated with cerebral ischemia. To decrease that risk, it is known to use deep hypothermic circulatory arrest (DHCA) to decrease metabolic demand during the circulatory arrest. Electroencephalographic monitoring (EEG), serial measurements of jugular bulb saturations (jvSO2) and cerebral oximetry based on near infrared spectroscopy can be used to identify cerebral ischemia. In the context of DHCA, however, only cerebral oximetry can be utilized to monitor a patient to detect ischemia during the arrest period itself. This is because isoelectricity caused by deep hypothermia makes EEG monitoring useless, and the circulatory arrest makes jvSO2 measurements unreliable. Consequently, cerebral oximetry currently provides the only technology that can be employed in the DHCA setting.
Current cerebral oximetry devices can provide real-time oxygen saturation information. They do not, however, possess the capability to predict the onset of cerebral ischemia.